This invention relates generally to agriculture and more particularly to a technique for retaining water and nutrients in the soil to assist in the growing of agricultural crops.
As long ago as 3150 B.C., when irrigation was introduced to the River Nile valley, there was the knowledge that crops require a consistent supply of water for the plant to reach optimal growth.
It has been stated by researchers that heavy clay soils lose b 70% of their trapped moisture through evaporation while very sandy soils lose 65% of their trapped moisture through gravitational leaching.
To limit gravitational leaching, one technique employed has been the placement of a layer of asphalt underground to retard the leaching. Although this technique did reduce leaching, the asphalt also restricted root growth extension and created a potential problem of a perched water table.
The leaching problem extends past water loss and into the loss of fertilizer chemicals which can find their way into the ground water before the crop has a chance to utilize them. Where groundwater contamination is pronounce, one solution is the use a plastic sheet under the soil's surface to retard leaching of moisture and chemicals into the underground water table. Again, this solution creates more problems than it solves by retarding root growth and by creating a perched water table.
In more modern times, the use of water absorbent polymers has become more widely used. The traditional "reasoning" on polymers is that they act as "water banks" or "reservoirs" for the crop to draw upon.
In U.S. Pat. No. 5,303,663, the use of polymers is discussed and the stated advantage is that the technology creates a "blanket" of moisture retaining particles for the plant roots. This blanket can hold only a certain amount of water which is insignificant to that required to satisfy a growing crop's moisture requirement.
In one controlled application, a five year old polymer blend installation into an alfalfa field has for five years demonstrated that a treated field produces approximately 35% more hay while using 50% less water and 50% less fertilizer than in an adjacent field which has not been treated.
Following the "reservoir" philosophy, with the absorption capacity of the polymer at 200-400 times, and at the recommended application rates of 20 pounds per acre in agriculture applications, the maximum water storage capacity is only 4000 pounds of water per acre. An active growing agricultural crop uses about 40,000 pounds of water per day. Six inches of saturated loam type soil holds about 400,000 pounds of water.
The polymer reservoir constitutes less than 2% of the retention in the loam. A 2% increase in water cannot account for the fifty percent reduction in water use experienced.
Obviously, the technological reasoning behind the use of polymers is flawed; and as such, optimal polymer use in agriculture cannot be obtained.
It is clear from the foregoing that there continues to be a need for effective control and utilization of irrigation water.